This invention relates to a railway car having crosstie connections with improved fatigue life and more particularly to an apparatus and method which reduce or eliminate stress related fatigue cracks in an associated weld between two structural members joined to each other at approximately a right angle.
All railroads have a maximum limit on the total amount of weight which may be safely placed upon the associated railway tracks. The total load carrying capability of railway tracks and railway cars may vary substantially depending upon various design parameters. Since there are other limits as to the total amount of weight which may be safely supported by a pair of tracks, there is a continuous ongoing desire within the railway industry to increase the weight of cargo or lading which may be transported within a railway car while at the same time reducing the unloaded or xe2x80x9clight weightxe2x80x9d of the respective railway car. Many railway cars used to transport freight often have a railway car underframe defined in part by a pair of side sills and a pair of end sills joined with each other in a generally elongated, rectangular configuration.
One or more transverse members may be attached to the side sills and spaced from each other intermediate the end sills. Such transverse members are typically provided to support the side sills and/or cargo carried by the associated railway car. For some applications such as well cars, transverse members which support cargo or lading are sometimes referred to as crossbearers. Transverse members which support associated side sills may sometimes be referred to as crossties.
During the past several years, railway cars have been developed for use in transporting various types of containers associated with intermodal transportation systems. Such railway cars often have a depressed floor section disposed between a pair of longitudinally extending side structures and transverse end structures. Such railway cars may sometimes be referred to as well cars. Multiple transverse members or crossties are typically disposed between the longitudinal side structures and spaced from each other intermediate the associated end structures. Some of the transverse members, often referred to as xe2x80x9cloadbearing cross members or crossbearersxe2x80x9d may be used to support containers or other types of lading carried within such well cars. Other transverse members, often referred to as crossties, may be used to provide structural support for the associated longitudinal side structures and more particularly the associated side sills. U.S. Pat. No. 4,805,539 entitled xe2x80x9cWell Car End Structure Having Frameless Radial Truckxe2x80x9d and U.S. Pat. No. 5,562,046 entitled xe2x80x9cLoad Bearing Cross Bearer Connectionxe2x80x9d provide examples of such well cars and associated transverse members.
Well cars may sometimes be described as a flatcar with a depression or opening in the center to allow the load to extend below the normal floor level so that the load will not extend above applicable overhead clearance limits. The configuration of a typical well car generally results in the lading or cargo placing multi-directional loads on the associated side sills. Crossties are often provided to cooperate with the side sills to distribute and transmit loads associated with transporting lading by the well car. These loads typically cause relatively high stresses in the structural components of the side sill and crossties. Often welds are formed between the ends of a typical crosstie and respective portions of the side sills of the railway car. The configuration of the end of a typical crosstie and adjacent portion of a side sill frequently results in notches being formed at the end of one or more welds used to connect the crosstie with the side sill. The notches may function as stress risers which in combination with relative high stresses present in the side sill substantially reduce the fatigue life of the associated weld and compromise the integrity of the connection formed between the crosstie and side sill.
Various types of mechanical fasteners, fittings and welding techniques have been used to join a first structural member to a second structural member at an angle of approximately ninety degrees relative to each other. For some applications an appropriately sized end plate has been attached to one end of a first structural member for use in providing a desired connection with a second structural member.
The present invention includes an apparatus and method to form a weld attachment between two structural members joined to each other at approximately a right angle and minimizes potential for fatigue cracking of an associated weld. Transverse members of a railway car underframe and associated side sills are examples of such structural members.
One aspect of the present invention includes a transverse member or crosstie having end plates incorporating teachings of the present invention secured to opposite ends thereof for use in connecting the crosstie with respective portions of an associated railway car side sills. The end plates are preferably substantially enlarged as compared to the cross section of the associated transverse member to increase the amount of weld contact between the resulting weld attachment and respective portions of the side sills. The configuration and size of the end plates and resulting weld attachment are preferably selected, in accordance with teachings of the present invention, to minimize the effects of any abrupt change in cross section between the transverse member and the side sills.
For one embodiment a railway car is provided with a plurality of weld attachments having end plates and respective bolts extending through the end plates and adjacent portions of the railway car. Coupling a respective bolt to the end plate and adjacent portions of the railway car proximate each end of the associated weld attachment substantially reduces or eliminates stress risers, and thus reduces or eliminates any tendency for one or more fatigue cracks to develop in the vicinity of an associated weld. When loads are transferred between a first structural member such as a crosstie and a second structural member such as a side sill, the bolts will preferably absorb or pickup a substantial amount of the load being transferred and reduce peak stresses at the ends of the associated weld. The present invention allows a weld attachment and associated weld to join a crosstie with an associated side sill in a manner that substantially reduces or eliminates any potential for fatigue cracking of the weld.
Technical benefits include using an end plate formed as part of a press fitting in accordance with teachings of the present invention to provide a weld attachment or weldment which substantially increases the fatigue life of an associated weld. The end plate may also be formed as a part of a casting or forging to provide a weld attachment or weldment incorporating teachings of the present invention. The present invention allows selecting the optimum configuration and dimensions for an end plate and resulting weld attachment to minimize stress risers and any corresponding tendency of an associated weld to develop one or more fatigue cracks. For one embodiment the pressed fitting is preferably flared along each side to provide increased weld area and to also reduce the effect of any abrupt change in cross section between a first structural member connected to a second structural member at approximately a right angle.